The plant may for example be a circulation plant where the fluid medium after being heated gives off heat to or after being cooled takes up heat from the surroundings or to/from a secondary fluid medium through at least one heat exchanger or a similar object. Such plants are generally called heating plants or cooling plants (air-conditioning), respectively.
Such a plant is known from U.S. Pat. No. 5,178,324 and is configured in such a manner that it is possible to control the flow in the whole plant, in a single part of the plant or in several sections of a plant being divided into zones.
This plant comprises several heat exchangers, each provided with a valve, the said heat exchangers being arranged to be placed in a number of at least one in each their room in a building where the differential pressure valve is provided in the plant piping.
However, the known plant is encumbered with the drawback that it is controlled solely by the flow in the plant by means of the differential pressure valve. Consequently, the valve cannot operate dynamically and nor can it be adjusted accurately to a predetermined flow in the plant in order to achieve an improved operating economy, if the temperature conditions or the winds inside or outside the building change. Therefore, if such changes occur it will be necessary to intervene to manually bring the closing member into another position.
From U.S. Pat. Nos. 5,213,303, 3,112,094 and 4,180,236 are moreover known differential pressure valves of the type described alone. The known valves are configured to operate statically and therefore they cannot limit the flow to a certain flow in a plant being provided with the valves to ensure a hydraulic balance in the plant. Nor are the valves configured in such a manner that a modification can be carried out while they are mounted. Besides, for reasons of economy it is generally necessary to replace the valves by new valves instead of rebuilding them.
Therefore, it is the object of the present invention to produce a differential pressure valve which can replace the known differential pressure valve as a matter of course, or to indicate such modifications of the known differential pressure valve that these modifications can be mounted on or inserted in the known differential pressure valve without dismounting it to the effect that by means of the modified differential pressure valve the possibility is provided of limiting the flow in the plant automatically to a predetermined, adjustable maximum size in connection with a dynamic reduction of the flow which automatically ensures the hydraulic balance in a versatile plant.